Gl1200 backfire


Information and questions on GL1200 Goldwings (1984-1987)
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dtwing
Posts: 2
Joined: Fri Dec 07, 2012 6:31 pm
Location: Houston, Texas
Motorcycle: 1987 GL1200A Aspencade

Gl1200 backfire

Postby dtwing » Fri Dec 07, 2012 7:44 pm



My 1987 GL1200A sat for several months without riding. I went to start it up and it wouldn't. I replaced the battery. Cranked and cranked, but wouldn't start. Instead gas came out the overflow vents. So then I rebuilt the carbs with a Randakk kit and replaced the spark plugs, caps, and wires. Started it up, set the pilot screws and synched the carbs. On the test ride it ran rough and seemed to lack power. Then work got in the way and it sat a few weeks. I got back to it today. I fiddled with the pilot screws some more. Still runs rough - has a miss. Adjusting the pilot screws on #2 and #4 cylinders has little effect on the RPM. Cylinder #4 screw has some effect, but #2 has no effect at all. Also noticed that opening the synch port on #2 to atmosphere has no effect on rpm. I pulled the plug caps one at a time while running and all are cylinders are firing. It has a slight backfire/pop at low speed. It has a bad pop/backfire as the RPM slows to around 2900. Compression is #1 = 185 psi, #3 = 187 psi, #2 = 185 psi, #4 = 175 psi.

So where do I start? Do I open the carbs back up and try cleaning again? Do I pull the left side head?



bustedwing
Posts: 1052
Joined: Wed Nov 30, 2011 4:17 pm
Location: Hermansville, Mich
Motorcycle: 1990 Gold wing Trike
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Re: Gl1200 backfire

Postby bustedwing » Fri Dec 07, 2012 10:47 pm

Sounds like you have bad fuel or dirty lines someplace, try running Seafoam thru it for a few tanks of fuel to get it cleaned out. It will not run any better while the Seafoam is working itself thru the system because it is taking the bad gas with it but should run better after the Seafoam is done and clean fuel is put in the tank.
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dtwing
Posts: 2
Joined: Fri Dec 07, 2012 6:31 pm
Location: Houston, Texas
Motorcycle: 1987 GL1200A Aspencade

Re: Gl1200 backfire

Postby dtwing » Sat Dec 08, 2012 10:06 pm

As part of the carb overhaul I replaced the fuel filter and drained out all of the old gas. There could still be something clogging up the works, but I tried to get it all cleaned up during the carb rebuild.

goldminerusa
Posts: 245
Joined: Wed Mar 07, 2012 8:20 am
Location: Southern NH, home again!
Motorcycle: 1982 gl 1100standard, 1983 1000c

Re: Gl1200 backfire

Postby goldminerusa » Fri Dec 14, 2012 7:06 pm

Is the bike backfiring thru the carbs or the exhaust? Thru the carbs should indicate theres an intake valve slightly open when the ign. fires, thru the muffler is an exhaust valve open at firing. I`d pull the valve covers and check the valvetrain, same with the cam belts, a stretched belt could keep a valve from closing. you`ve addressed the fuel system, time to look elsewhere. check the ignition too, the valvetrain could be right but a cylinder is firing too early/late.




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